var canvas=document.getElementById("myCanvas");
var cxt=canvas.getContext("2d");
cxt.fillStyle="pink";
var i=0;
setInterval(jindu,10);
function jindu(){
    /*	  cxt.clearRect(0,0,600,600);*/
    cxt.fillRect(i,i,40,40);
    cxt.fillRect(600-i,600-i,40,40);
    cxt.fillRect(i,600-i,40,40);
    cxt.fillRect(600-i,i,40,40);
    i++;
}
